Psychological distress as a risk factor for dementia after the 2004 Niigata-Chuetsu earthquake in Japan

A large earthquake can cause extreme stress and may adversely affect cognitive function in humans. We aimed to examine a possible association between psychological distress and incident dementia after the 2004 Niigata-Chuetsu earthquake in Japan.

This is a retrospective cohort study followed participants for 10-12 years. Subjects were 6,012 residents in 2005, 5,424 in 2006, and 5,687 in 2007 (age ≥40 years) living in Ojiya city who participated in the annual health check examinations after the 2004 Niigata-Chuetsu earthquake. Psychological distress was assessed using the Kessler Psychological Distress Scale (K10), and individuals with a K10 score ≥10 were considered to have psychological distress. Incident dementia cases were identified from a long-term care insurance database of the local government during the follow-up period. We evaluated hazard ratios (HRs) of psychological distress for incident dementia in each year, unadjusted and adjusted for covariates, including sex, age, occupation, BMI, and property damage of residential area.

The average age of the subjects was 64.6 years in 2005, 64.6 in 2006, and 65.2 in 2007. Adjusted HRs were significantly higher (HR = 1.20-1.66) in the psychological distress group than in the reference group in each year. In particular, adjusted HR was high (HR = 2.89) in those with psychological distress in all three years (2005-2007).

Psychological distress, especially persistent distress, is a risk factor for incident dementia in victims of large disasters.